Venting basement DWV system

I'm trying to figure out how to vent my basement bath and shower drains. In WA state code says you can't roll a vent more than 45 degrees until 6 inches above the flood line of the highest fixture? If I have a drain in the basement along an outside wall that I'm running straight down the middle of the bathroom (so there is no access to a wall to run a vent in any other place in the required distance) and I'm trying to vent along the wall back around the room to the vent, what kind of fittings would I use? Without running the line a few feet close to horizontal I'm not sure how it is physically possible. This is a mock up (a poor one), the wall the line crosses over is too far to meet code so I have to vent out the back. The drain for the bath is going to be a few feet from the wall at the bottom and the other drain is going to be a few feet from the wall on the left.

For starters, when the tub drains, unless there is a vent for both the shower and the tub, that are separate, the p-trap on the shower is going to siphon dry when the tub drains.

Washington State UPC
You can run a 2" trap arm 60" before the vent
and for a 1.5" trap arm, 42" before the vent.
The revents need to be 42" above the floor.
In this case, the shower and the tub have vents that can be tied in together at 42" above the floor.

Thank you for reply. I was planning on venting them separately and tying them together eventually at least 42" above the floor. Is it possible to vent the tub on the back wall? And the shower on the left wall? If so, how is it possible without running the vent horizontal a short distance? What fittings would allow this to happen or how can I run the lines so I can stay in code when rolling the vent?